A liquid crystal display (LCD), with the advantages of high display quality, low costs, portability and the like, is the most widely used flat panel display at present. With a high resolution color screen, the liquid crystal display has gradually become a widely used display of various electronic devices, such as mobile phones, personal digital assistants (PDA), digital cameras, computers or laptops.
A currently widely used LCD generally consists of an upper substrate, a lower substrate and a middle layer of liquid crystals, wherein the substrates each comprise a glass plate, electrodes, and so on. Moreover, a conventional LCD panel includes a color filter substrate, a thin film transistor (TFT) array substrate, and a liquid crystal layer configured therebetween.
In recent years, techniques are further proposed, wherein a color filter layer is directly integrated on a TFT substrate (“Color Filter on Array”; COA or TFT array substrate), or a black matrix layer is arranged on a TFT substrate (“Black Matrix on Array; BOA). In addition, a fringe field switching (FFS) technique is also proposed, wherein, for example, a COA substrate (or a BOA substrate) is assembled with an opposite substrate without a color filter layer or a black matrix layer, and then liquid crystal molecules are filled into the space between the two substrates to form an LCD panel. Since the color filter layer forms merely on the TFT substrate directly, no alignment errors will be generated. Moreover, this LCD panel has better resolution and higher aperture ratio of pixels.
Generally, spacers are arranged between the two substrates of an LCD panel. The spacers are mainly used to maintain the distance between the upper and lower substrates of the LCD, so as to provide a certain space for filling liquid crystals. Currently, said spacers are mainly placed between said two substrates in a dispersed manner. However, contrast, resolution and viewing angles of the LCD will be negatively influenced if the spacers are dispersed inappropriately. In particular, with the enlargement of LCD panels, even distribution of spacers has become more and more important.
There are two traditional methods for providing spacers: one is using uniform spacers (as shown in FIG. 1), while the other is using hybrid spacers (as shown in FIG. 2), i.e. creating side spacers through weak exposure.
According to the first method, all spacers have the same height. The advantages of this type of spacers are of larger taper angles, narrower width of black matrix, and higher aperture ratio and penetration ratio, while the disadvantage thereof is that the liquid crystal margin is limited due to spacers of one single height.
According to the second method, all spacers have different heights. As spacers include higher main spacers and lower side spacers, this method enables a larger liquid crystal margin (as shown in FIG. 2), while the disadvantages thereof are smaller taper angle and wider width for the side spacers formed, and larger coverage width of the required black matrix, which will affect the aperture ratio and penetration ratio, or increase cost.